Extensions will likely need state, or other abilities, not provided currently by the X monad core. One approach to solve this is to add a cheap symbol table to the XState field, allowing extensions to stick their own modifiable global state. A more intriguing, and perhaps, dangerous, idea, is to allow arbitrary monad transformers to be specified by user contributions. The problem of adding state then becomes a matter of defining a StateT transformer. But it also opens up the option of using ReaderT for config values, or even hmm, ContT for check pointing state (!). By default the outer monad would be IdentityT. Downsides are unexplored, the main being: * how do you combine state, or monad state, from multiple extensions? There are cheap solutions, as we see above, but the idea of user customised monad transformers -- redefining the entire application's behaviour -- is very tempting. Here's the patch for user-specified UserT transformers, to ponder. New patches: [User-definable monad transformers: most general state/behaviour extension we can think of Don Stewart <dons@cse.unsw.edu.au>**20070601050546] { hunk ./Config.hs 30 +import IdentityT hunk ./Config.hs 146 +------------------------------------------------------------------------ + +-- default monad transformer to run xmonad in: +type UserT = IdentityT + +-- default way to run the monad transformer +runUserT :: Monad m => UserT m a -> m a +runUserT = runIdentityT + +-- Example, user defined state: +-- type UserT = StateT () +-- runUserT m = evalStateT m () + hunk ./Config.hs-boot 2 +import IdentityT hunk ./Config.hs-boot 8 +runUserT :: Monad m => UserT m a -> m a +type UserT = IdentityT addfile ./IdentityT.hs hunk ./IdentityT.hs 1 +----------------------------------------------------------------------------- +-- | +-- Module : Identity.hs +-- Copyright : (c) Spencer Janssen 2007 +-- License : BSD3-style (see LICENSE) +-- +-- Maintainer : dons@cse.unsw.edu.au +-- Stability : stable +-- Portability : portable +-- +module IdentityT where + +import Control.Monad.Trans + +-- +-- IdentityT , a parameterisable identity monad, with an inner monad +-- The user's default monad transformer +-- + +newtype IdentityT m a = IdentityT { runIdentityT :: m a } + +instance (Functor m, Monad m) => Functor (IdentityT m) where + fmap f = IdentityT . fmap f . runIdentityT + +instance (Monad m) => Monad (IdentityT m) where + return = IdentityT . return + m >>= k = IdentityT $ runIdentityT . k =<< runIdentityT m + fail msg = IdentityT $ fail msg + +instance (MonadIO m) => MonadIO (IdentityT m) where + liftIO = IdentityT . liftIO hunk ./XMonad.hs 24 +import {-# SOURCE #-} Config (UserT, runUserT) hunk ./XMonad.hs 73 -newtype X a = X (ReaderT XConf (StateT XState IO) a) +newtype X a = X (ReaderT XConf (StateT XState (UserT IO)) a) hunk ./XMonad.hs 79 -runX c st (X a) = runStateT (runReaderT a c) st >> return () +runX c st (X a) = runUserT (runStateT (runReaderT a c) st) >> return () } Context: [ignore numlock/capslock on mouse bindings Jason Creighton <jcreigh@gmail.com>**20070601015137] [now we handle transients properly, and restack windows, refresh from focus is ok Don Stewart <dons@cse.unsw.edu.au>**20070601022329] [Rename withWorkspace to withWindowSet. glasser@mit.edu**20070601001325] [Revert accidental change to border color Spencer Janssen <sjanssen@cse.unl.edu>**20070531145509] [comments on why fullscreen tiling doesn't work with `implicit' floating Don Stewart <dons@cse.unsw.edu.au>**20070531090537] [clean up mouse code a bit Don Stewart <dons@cse.unsw.edu.au>**20070531085308] [first shot at a floating layer Jason Creighton <jcreigh@gmail.com>**20070531044733 This is a first attempting at a floating layer: mod-button1: move window mod-button2: swapMaster mod-button3: resize window mod-t: make floating window tiled again Moving or resizing a window automatically makes it floating. Known issues: Hard to manage stacking order. You can promote a window to move it to the top, (which you can do with mod-button2) but it should be easier than that. Moving a window by dragging it to a different Xinerama screen does not move it to that workspace. Code is ugly. ] [remove LOC cap (but still print count after tests) Jason Creighton <jcreigh@gmail.com>**20070531043417] [TAG 0.2 Spencer Janssen <sjanssen@cse.unl.edu>**20070531010004] Patch bundle hash: 864d7acd95d9f45379cef7d18919783971b243f0